Multi-ratio clutch

ABSTRACT

An improved clutch has a distinct force ratio for holding than it does for release. A distinct ratio is achieved by having an abutment surface between a retainer and a diaphragm spring be positioned radially outward from a contact location between a release sleeve and the diaphragm spring for releasing the clutch. The retainer is separately axially movable relative to the release sleeve, and surrounds the release sleeve. In this way, the holding force is applied at a lever distance from an axial center line of the clutch which is greater than the distance to the point of contact for release of the diaphragm spring. This provides both a higher holding force and yet a lower release force.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a clutch having a higher holding forceand a lower release force through the use of distinct ratios for holdingand release force.

[0002] Clutches are utilized to selectively transmit or releaserotational drive between components in a vehicle driveline. Typically, aclutch is positioned between a vehicle engine and a vehicletransmission. In known clutches, an element is selectively biasedagainst a pressure plate to force the pressure plate to squeeze at leasttwo interleaved disks. One of the disks is connected to rotate with ashaft to be driven and the other disk is fixed to rotate with a clutchcover. The clutch cover is typically connected to the engine to bedriven.

[0003] In the prior art clutch, a retainer member is connected to movewith a release sleeve by a generally conical inner flange on the releasesleeve. The retainer rotates with the clutch cover, and thus is able torotate relative to the sleeve, however, upon axial movement of thesleeve, the retainer typically also moves.

[0004] In the prior art clutch a component known as a diaphragm springforces the retainer in a direction such that it pivots a series oflevers to force the pressure plate to squeeze the disks. The diaphragmspring is biased towards a relaxed position, and in trying to movetowards its relaxed position its contacts abutment surface on theretainer forcing the retainer to the engaged position at which it causesthe levers to hold the pressure plates to squeeze the disks.

[0005] When it is desired to release the clutch, the release sleeve ismoved to pull the diaphragm spring in a direction allowing the retainerto move away from the engaged position. In the prior art, the point ofcommunication of force from the diaphragm spring holding the retainer inits locked position and point of contact between the retainer and thediaphragm spring are the same.

[0006] It would be desirable to have a holding force which is high, anda release force which is low. These two desires have resulted intrade-offs between optimum forces for the two.

SUMMARY OF THE INVENTION

[0007] In a disclosed embodiment of this invention, the point of contactbetween the diaphragm spring and the release member is distinct from thepoint of contact of the diaphragm spring and the retainer biasing theretainer to its holding position. In this way, a large holding force canbe created with a much lower release force.

[0008] While this application may refer to “point” of contact, of coursethe contact is actually over a surface area. When the application claimsuse the terms “point” or “surface” of contact, this should not be readas limiting in any fashion, and would be met by a line contact or across-sectional area contact, or other contacts.

[0009] In a preferred embodiment the retainer member is connected to bepositioned separate from the release sleeve. The release sleeve contactsa radially inner part of the diaphragm spring, and causes the diaphragmspring to be pulled to the release position. When the diaphragm springis pulled to its release position it also pulls the retainer to thereleased position. The connection between the diaphragm spring and therelease sleeve being at the radially inner end of the diaphragm springresults in a relatively low release force.

[0010] However, the connection between the retainer and the diaphragmspring is spaced radially outward from the release point of contact. Inthis fashion, a multiplier effect from the diaphragm spring force isachieved. The holding force is thus much greater than the release force.

[0011] The retainer being separately movable relative to the releasesleeve facilitates this benefit.

[0012] These and other features of the present invention can be bestunderstood from the following specification and drawings, the followingof which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a cross-sectional view to an inventive clutch, shownsomewhat schematically.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0014] A clutch 20 is illustrated in FIG. 1 having a clutch cover 22 tobe driven such as by an engine. A release bearing 24 is connected to arelease sleeve 25. The release sleeve 25 has a step 26 at an axiallyinner end. A coil spring 28 is biased between the bearing 24 and aninner end 30 of a diaphragm spring 32. The spring 28 holds the step 26against the inner end 30 of the diaphragm spring 32 when the releasesleeve is not being pulled to its release position.

[0015] An outer end 34 of the diaphragm spring 32 fits against anabutment surface 36 on the clutch cover 22. A retainer member 38 ispositioned radially outwardly of the release sleeve 25. An innerdiameter 37 of the retainer is shown to be greater than an outerdiameter of the step 26 such that the release sleeve 25 movesindependently of the retainer 38. A pin 39 extends through a bore 31 inthe retainer ensuring that the retainer 38 rotates with the clutch cover22.

[0016] An abutment surface 40 on the retainer engages the diaphragmspring 32 at 41. A connection member 42 is shown schematically, and willallow limited axial movement between the retainer 38 and the diaphragmspring 32, but ensure that when the diaphragm spring 32 is driven to theright as shown in FIG. 1, it brings retainer 38 along. A worker in thisart would recognize how to connect the two in such a fashion such asthrough straps, etc., as are known for other applications.

[0017] A groove 44 in the retainer 38 receives a lever 48 which engagesa pressure plate 46. As known, in the illustrated position, thediaphragm spring 32 is held away from its relaxed position. It thusapplies a force tending to move surface 40 towards the left as shown inFIG. 1. This causes pivoting movement of the lever 48 to the illustratedposition. In the illustrated position the pressure plate 46 is caused toclamp the disks 50 and 52 which are connected to rotate with the clutchcover and a shaft to be driven, as known.

[0018] Inventive aspects of this invention include the positioning ofabutment surface 40 outwardly, the use of a surface 26 on the sleeve 25for release contact, and the fact that the retainer 38 is separate fromthe release sleeve 25. When the clutch is driven to its engaged positionsuch as is illustrated, a force is applied from point 41 throughabutment surface 40. This force is relatively great in that the distanceoutwardly from an axial center line X of the clutch serves to multiplythe force compared to the force that would be applied at a radiallyinner end of the diaphragm spring 32. On the other hand, the releaseforce only need overcome the force at the radially inner end 30 of thediaphragm spring 32. When it is desired to release the clutch, therelease sleeve 25 is moved to the right from the illustrated position.The step 26 pulls the diaphragm spring 30 to the right. The connection42 will cause the retainer 38 to also move to the right. This will relaxthe force from the pressure plate 46 allowing the disks 50 and 52 tomove out of engagement.

[0019] The present invention thus provides two distinct force ratioswith the same basic structure. A designer of clutches is now able tobetter optimize a clutch by providing a relatively high holding forcewith a relatively low release force.

[0020] Although a preferred embodiment of this invention has beendisclosed, a worker in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason the following claims should be studied.

1. A clutch comprising: a release sleeve axially movable along an axisof rotation; a clutch cover to be driven for rotation about said axis ofrotation, and a pressure plate for rotation with said clutch cover; adiaphragm spring for applying a holding force to a retainer member at anabutment surface, said retainer member being attached for rotation withsaid clutch cover, said retainer including at least one lever forselectively applying a force against said pressure plate causing a diskto be operably connected to said clutch cover, said retainer beingmovable to a release position at which said at least one lever allowssaid pressure plate to move to a position at which said disk does notrotate with said clutch cover; and said diaphragm spring biasing saidretainer member to said engaged position, and a release surface forselectively moving said diaphragm spring to a position at which saidretainer member can move to said disengaged position, said releasesurface being positioned radially inward from said first abutmentsurface.
 2. A clutch as recited in claim 1, wherein said retainer isseparately axially movable relative to said release sleeve, with saidabutment surface being on said retainer member, and said release surfacebeing on said release sleeve.
 3. A clutch as recited in claim 2, whereinsaid release sleeve has an axially inner step contacting a radiallyinner end of said diaphragm spring, a coil spring causing said step tobe in contact with said radially inner end of said diaphragm spring. 4.A clutch as recited in claim 3, wherein a radially intermediate portionof said diaphragm spring contacts said abutment surface on saidretainer, and forces said retainer to said engaged position.
 5. A clutchas recited in claim 3, wherein an inner peripheral bore on said retainerhas a greater inner diameter than an outer diameter of said step on saidrelease sleeve such that said release sleeve can move within said boreon said retainer.
 6. A clutch as recited in claim 1, wherein saidretainer is connected for limited axial movement relative to saiddiaphragm spring.
 7. A clutch comprising: a release sleeve axiallymovable along an axis of rotation; a clutch cover to be driven forrotation about said axis of rotation, and a pressure plate for rotationwith said clutch cover; a diaphragm spring for applying a holding forceto a retainer member at an abutment surface, said retainer beingattached for rotation with said clutch cover, said retainer including aplurality of levers for selectively applying a force against saidpressure plate causing a disk to be operably connected to said clutchcover, said retainer being movable to a release position at which saidat least one lever allows said pressure plate to move to a position atwhich said disk does not rotate with said clutch cover; said diaphragmspring biasing said retainer member to said engaged position, and arelease surface for selectively moving said diaphragm spring to aposition at which said retainer member can move to said disengagedposition, said release surface being positioned radially inward fromsaid first abutment surface; and said retainer being separately axiallymovable relative to said release sleeve, with said abutment surfacebeing on said retainer and said release surface being on said releasesleeve, said retainer being connected for limited axial movementrelative to said diaphragm spring, and said release sleeve having anaxially inner stop contacting a radially inner end of said diaphragmspring, a coil spring causing some said stop to be in contact with saidradially inner end of said diaphragm spring, a radially intermediateportion of said diaphragm contacting said abutment surface on saidretainer, and forcing said retainer to said engaged position, and aninner peripheral bore of said retainer having a greater inner diameterthan an outer diameter of said step of said release sleeve such thatsaid release sleeve can move within said bore on said retainer.